Hannah Mary Fry was born in Essex, England, on 21 February 1984. The middle of three sisters, she was raised in Hoddesdon and Ware, Hertfordshire. She is of English and Irish heritage: her father was an English factory worker making hydraulic lifts for lorries and her Irish Catholic mother stayed at home. One summer, aged about 11, her mother made her solve a page of problems in a mathematics textbook each day of the holiday, putting her ahead of other pupils when she went back to school. She attended Presdales School in Ware, where a teacher inspired her to study mathematics.

She graduated from University College London (UCL) with a degree in mathematics. In 2011, she completed her thesis under the supervision of Frank T. Smith and was awarded a PhD from UCL for research on fluid dynamics and the Navier–Stokes equations. Fry was appointed as a lecturer at UCL in 2012, working at the UCL Centre for Advanced Spatial Analysis. She was later appointed senior lecturer, then professor in the Mathematics of Cities.

Her research applies to a wide range of social problems and questions, from shopping and transport to urban crime, riots and terrorism. In 2023 the new series The Future with Hannah Fry launched on Bloomberg in February, bringing her signature intellectual heft and insight to American audiences, questioning our collective future and what we want it to look like.

In 2020, she was diagnosed with cervical cancer and underwent a radical hysterectomy. She wrote and presented the documentary Making Sense of Cancer with Hannah Fry for BBC Two’s Horizon about her treatment and its long-term effects, which included lymphoedema. Fry subsequently had lymphaticovenular anastomosis, a reconstructive surgery. Fry lives in South London.